Dartmouth BASIC file formats

Neither machine had a cassette deck, a disc a user could reach or a native program container. What each had was the punch and reader built into the Teletype Model 33 ASR, so there is exactly one export apiece — a paper tape, written as plain text in a .txt file. It is text, so it opens straight back through the ordinary file path and needs no import format of its own. No export here carries memory blocks, because both machines are offered as BASIC only and neither has any.

For the shared editor .txt, .zip project bundle, escape notation and the cross-machine format overview, see the file formats overview. See also the Dartmouth BASIC reference and its escape codes.

The GE-235

GE-235 paper tape .txt

How a program left a machine with no storage of its own: LIST with the Teletype's punch running, and the reader feeds the tape back a line at a time.

The export is the listing as the tape carries it rather than as the editor shows it — the line number, one space, then the body with its blanks removed, since the compiler deletes them before it reads a line anyway. Blank editor lines are gone, and the lines are in the order they were typed. Each line ends with a carriage return and a line feed, as a Teletype needs; the editor's own bare line feed would leave the carriage where it was.

Two things a reader coming from the Altair's paper tape will notice, and both follow from this machine's codes not being ASCII:

• {0oNN} escapes stay spelled out. On a machine whose codes are ASCII an escape can resolve to the byte it names, because that byte is what the punch wrote. Here it would be a six-bit code no text file could show, and the file would stop being openable. Spelled out, it survives the round trip.
• Nothing closes the file. The tape's own terminator is the end-of-message code, which has no printable form; the end of the file says the same thing.

The power operator is written as the up arrow ↑ it is typed as. That is the character the Teletype's keyboard had, and the revision of ASCII that spells it ^ is two years younger than the machine — so the tape carries the character the machine had, which is also the one the editor reads back.

Cassette audio

There is none. The GE-235 had no tape interface to model: a user reached it over a telephone line from a teletype, and the only thing that recorded a program was that teletype's paper-tape punch, described above. The IDE offers no .wav export and no cassette import for this machine.

The GE-635

GE-635 paper tape .txt

The same procedure on the same terminal, and the manual gives it in full: LISTNH with the paper-tape unit switched on to punch one, then NEW, the file name, TAPE and KEY to read one back.

The export is again the listing as the tape carries it — the line number, one space, the trimmed body — with blank editor lines gone, the lines in the order they were typed, and each closed by the carriage return and line feed a Teletype needs. ↑ is written as itself here too: it is code 94, the character the ASR-33's key face carries and this BASIC raises to a power with, rather than the ^ a later ASCII puts there.

Two things follow from that, and only the second is a difference from the GE-235's tape:

• A {0xNN} escape stays spelled out, exactly as the GE-235's {0oNN} does. This machine's codes are ASCII, so unlike its sibling it could put the byte itself on the tape — but a .txt is opened again as text, and a code the Teletype cannot print is not a character that can be typed back in. Spelled out, it survives the round trip; resolved, it would make a file the IDE could no longer read. The same goes for ↑ and ←, whose codes a later ASCII reads as ^ and _.
• Nothing closes the file, and for a different reason from the GE-235's: there is no end-of-message code to leave out. ASCII has none and the manual names none, so the end of the file says the same thing.

Cassette audio

There is none, for the same reason as on the GE-235. The machine had no tape interface to model — a user reached it over a telephone line — and the only thing that recorded a program was the teletype's own paper-tape punch. The IDE offers no .wav export and no cassette import for this machine.